Not until 2:30 p.m. on July 3, 1863, did the ear-splitting bombardment finally slacken on the rolling farmland of southern Pennsylvania. Nothing like it had ever been experienced before in America, or would be again. “The very ground shook and trembled,” wrote a witness, “and the smoke of the guns rolled out of the valley as tho there were thousands of acres of timber on fire.” For close to 90 minutes, 163 Confederate cannon had blanketed the Union battleline in a bedlam thick with smoke and deadly iron fragments. The Union guns replied at a more measured pace, saving ammunition for what was to come, but still added their measure to the unendurable din.

Then, as the thunder died away, it appeared that a god of battles was stage-managing the scene: a breeze sprang up to part the thick curtains of smoke and reveal ordered lines of Confederate troops in their thousands striding out of the woods across the open fields toward Cemetery Ridge. Up on the ridgeline the ranked Union soldiers took in the sight and involuntarily cried out, “Here they come! Here comes the infantry!”

“None on that crest now need be told that the enemy is advancing,” wrote Union Lt. Frank Haskell. “Every eye could see his legions, an overwhelming resistless tide of an ocean of armed men sweeping upon us!” What history records as Pickett’s Charge would climax the great three-day struggle ominously north of Washington and make or break Robert E. Lee’s attempt to gain a decisive victory on northern soil. On the first day Lee had won the initial round of fighting; on the second day his attacks on both Union flanks only narrowly failed; now, after an unprecedented bombardment intended to pulverize the defenses, he thrust 13,000 infantrymen against the Union center.

But the management and direction of the bombardment had been faulty—even the ammunition was deficient—leaving the defenders’ lines largely intact. Union Gen. George G. Meade, only days in command of the Army of the Potomac, had prepared well to meet the charge, especially with his own massed artillery. Meade and his artillery chief, Henry J. Hunt, ordered their guns to cease fire to lull the Confederates into thinking that the way was clear for their infantry. And then Hunt’s guns—more than 100 of them—did open, slaughtering the stunned infantry: “They were at once enveloped in a dense cloud of smoke and dust. Arms, heads, blankets, guns and knapsacks were thrown and tossed into the clear air. . . . A moan went up from the field, distinctly to be heard amid the storm of battle.”

Soon both the attackers’ flanks had been savagely beaten in by the Union batteries, wrecking Pickett’s Charge beyond recall even before the Union infantry finished the fight. The 20th Massachusetts, for example, took careful aim at the Confederate regiment advancing upon it “& then bowled them over like nine pins, picking out the colors first,” wrote Maj. Henry Livermore Abbott. “In two minutes there were only groups of two or three men running round wildly, like chickens with their heads off. We were cheering like mad.” In a final desperate lunge a few hundred attackers breached the Union center, only to be crushed by a counterattack. Abruptly it was over. Those attackers who had survived the terrible cannon and rifle fire drifted back toward the sheltering woods. What General Lee termed “the grand charge” was a grand failure, dashing his—and his new country’s—hopes for victory in Pennsylvania.

That same July 3, indeed that same midafternoon, almost a thousand miles south by southwest of Gettysburg, Union Gen. Ulysses S. Grant met with Confederate Gen. John C. Pemberton to arrange for the surrender of the latter’s besieged army in Vicksburg, Mississippi. The next day—four score and seven after the signing of the Declaration—bore witness to the two great Union victories. Pemberton officially surrendered Vicksburg, and Robert E. Lee started his beaten Army of Northern Virginia back to whence it had so recently set off with such high hopes. The Civil War would rage on for two more bloody years, but July 3, 1863, marked out at last the path to eventual Union triumph.